Usually, an air conditioning system comprises a fresh air inlet for drawing in fresh air from an environment of the vehicle. In addition, an air conditioning system is usually equipped with an air filter for filtering drawn-in fresh air, which is arranged in a fresh air path and separates therein a raw side from a clean side. On the raw side of the air filter, a deposition of water can occur, which may be contained in the fresh air, e.g. rain water or condensate. A water path conveys the separated water away. In addition, a water box can be optionally provided for collecting and conveying away water separated from the fresh air which, with respect to a fresh air flow occurring in the operation of the air conditioning system, is arranged upstream of the air filter, i.e. in the raw side of the fresh air path.
Such a water box forms a type of drainage, by means of which water which is carried in the fresh air can be discharged. The arrangement of such a drainage upstream of the air filter leads to a reduced stress of the air filter by water, which improves the service life of the air filter.
In addition, in such an air conditioning system it can be expedient to discharge the water, which is separated by means of such a drainage arrangement, together with condensation water which may occur within the air conditioning system. In an air conditioning system, condensation water can occur especially when a cooling device is arranged within the fresh air path, by means of which the drawn-in fresh air is cooled. Frequently here, the dew point of water is fallen below, whereby entrained water condenses and accumulates as liquid condensate. Such a cooling below the dew point of water is frequently desired within the air conditioning system, in order to bring about, alongside an efficient cooling of the fresh air, a drying of the fresh air at the same time.
A problem in the feeding of the drainage water to the condensate is the fact that the drainage water occurs on the raw side, whereas the condensate occurs on the clean side, so that impurities which are entrained in the drainage water can also contaminate a path serving for the discharging of the drainage water and of the condensation water. Furthermore, a drainage path leading the drainage water from the raw side to the clean side forms a bypass for bypassing the air filter, if no or only a little drainage water occurs, so that unpurified fresh air arrives at the clean side of the fresh air path via the drainage path. Hereby, the efficiency of the air filtration is reduced.